Isobutanol extraction of DNA

Hi there,
in order to concentrate DNA I need to do an isobutanol extraction followed by a diethyl ether extraction. I'm a little puzzled as to whether I should use BioUltra grade isobutanol that has been tested negative for DNAse/RNase or whether I can use the significantly cheaper isobutanol (what are the odds that DNAse survives isobutanol)?
Does anyone have any ideas on that?
Cheers,